Yes snakes do have tails. One of the caracteristic of all chordatas is that they have tail with postanal position. Therefor tail begins right after the anus and in most snakes it`s quite short (compare to the body length). In the legless lizards the tail is much longer comparing to the body (one way of distinguishing them). The ventral side of the snake tail has two rows of plates but only one row on the body (at least in Europe).

For the necks, probably. But only on the sceletal level. The first vertebra is definitely different from the others and makes the neck. But are the 2nd, 3rd and few others diferentiated I don`t know. I know that in snakes all body vertebras carry ribs.

You mean like viper which have two plated rows and the tail that can make sound??
and for the neck, is it mesured from the skull till the atlas bone (the first vertebrae segment)?
Oh..another question..many scientists said that in the early time, snake had legs but because of those legs they couldn't move fast so the degeneratd them..is it true??

Q: Why are chemists great for solving problems?
A: They have all the solutions.

Now I don`t know what you mean? I meant something like this OIIIIIIIIIIIII::::> I hope this is not more confusing. Rattles in the rattle snakes are made of the remainings of the old skin after the molting and does not have much to do with this.

I would say that atlas is the neck vertebra but do some others vertebras make neck with it I`m not sure.
Well yes. That is the current theory. The more slender body shape of snakes is more adept for fast moving through the grass than the leged body of a lizard. There are some groups of recent lizards in wich you can observe possible way of evolution (legs, big body => smaler legs, slender body => no legs, long and snakish body).

Also, I believe snakes have rudamentry legs, legs that have withered away thru evolution until only vestiges of them exist. The tail would be the part that is posterior to the "legs" as in other animals.